Because Obama's entire case would be based on being born in Hawaii where he would be compelled to produce proof of that fact.
So it really does not matter how the Obama birth certificate gets exposed. If it is proven Obama was not born in the US he's done. It's strike three - and goodbye Obama.
If Obama somehow proves that he was born in the US, even if it is by hook or crook, he still has a steep uphill battle to hoodwink everyone that jus soli is what a natural born citizen is.
It's the very reason you see the Obots on the Web who are so adamant and the huge effort by them to change the history of meaning and intent of the NBC clause to only be born to the soil.